In a mobile/indoor cellular radio communication system, a base station usually communicates with multiple mobile stations and functions as a bridge between mobiles and landline networks such as Local Area Networks (LANs). One of the major impairments in this radio communication environment is the multipath fading phenomenon. Antenna diversity techniques have been used to mitigate this multipath fading phenomenon. However, either transmitting or receiving antenna diversity techniques have been utilized in the past. These techniques have been utilized in a number of patents, each having certain advantages and disadvantages.
U.S. Pat. No. 4,761,822 to Maile discloses a burst-mode two-way communication system in which a plurality of transceivers at a base station share a common antenna arrangement. The common antenna arrangement consists of a plurality of antenna branches and antenna branch selection is made by an operative base station transceiver with regard to the received signal strength from a portable transceiver.
U.S. Pat. No. 4,953,197 to Kalwell, Jr. et al discloses a spatial diversity system in which a post-detection selection diversity scheme is used. The selection criteria are link quality, AGC level, and parity check errors. The main emphasis is on radio telephone communication applications.
U.S. Pat. No. 5,065,499 to Gordon et al discloses a switching antenna diversity scheme in which each antenna is coupled with circuitry to measure the instantaneous and average received signal strength. Antennas are switched if the current signal strength of selected antenna falls below a threshold calculated from the average value. Antennas are also switched if no switching occurs during a predetermined elapsed time. After the switch, a measured signal strength value is compared with the previous value and the system switches back to the previous antenna if the previous signal strength is higher.
U.S. Pat. No. 5,123,029 to Bantz et al which is assigned to the assignee of this invention, discloses a hybrid controlled access and random access schemes using frequency hopping spread spectrum communications techniques, and which is implemented in an indoor digital data radio communication system between mobile stations and a computer system. A hop in the frequency hopping spread spectrum, communication system is subdivided into two intervals so that different media-access protocols can be used in each interval. The protocol uses a centralized control scheme in one interval and a decentralized scheme in the other, and the intervals may be varied depending on the load of the system. U.S. Pat. No. 5,123,029 is incorporated herein by reference.
According to the present invention, both transmitting and receiving antenna diversity techniques are dynamically combined and coordinated to combat the multipath fading phenomena in a wireless radio communications system. That is, the invention is directed to a strategy for combining the use of a selection antenna diversity technique at a stationary unit such as a base station, and a selection or switching antenna diversity technique at a remote station efficiently, for data packet transmission in a wireless radio communications system.